Wide angle zoom lens system having shortened closeup focal length

ABSTRACT

A wide angle zoom lens system capable of photographing objects from infinity to a close distance while maintaining an excellent image-forming performance employs a first group which is a divergent lens group having a focusing function, and a second group which is a convergent lens group disposed rearwardly of the first group. The first group includes a divergent forward portion and a convergent rearward portion disposed with a predetermined spacing from the forward portion, the forward and rearward portions being movable relative to one another for focusing. The first and second groups are movable relative to each other to effect a magnification change.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the shortening of the closeup focal length ofa zoom lens system, particularly, a wide angle zoom lens system.

2. Description of the Prior Art

A zoom lens system covering a wide angle of view, the so-calledtwo-group wide angle zoom lens which comprises two groups, i.e., a firstgroup which is a divergent lens group and a second group which is aconvergent lens group, has recently been developed. Various problemswhich have been unavoidable in conventional wide angle zoom lenses, suchas variations in spherical aberration, coma and astigmatism resultingfrom zooming, particularly, significant negative distortion on the shortfocal length side, have been solved. Recent years have seen the adventof wide angle zoom lenses having high performance. However, if thediameter of the forward lens is reduced, or if the entire lens system isarranged in a compact form, the aforementioned variations in aberrationscannot always be corrected satisfactorily. Particularly on the longfocal length side, spherical aberration becomes considerablyover-corrected and if the first group is moved forwardly to effectfocusing upon an object which is close, the tendency towardover-correction becomes more pronounced, and results in extremeover-correction of spherical aberration. Therefore, in a wide angle zoomlens system comprising a divergent group and a convergent group, it hasbeen difficult to enhance the image-forming performance of close rangeobjects, and it has been unavoidably necessary to confine the closeupfocal length to a relatively long distance.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a wide angle zoom lenssystem which comprises two groups, i.e., a divergent group and aconvergent group, and in which the closeup focal length is shortened,and which has an improved close distance performance.

Briefly stated, a wide angle zoom lens system in accordance with theinvention, which is capable of photographing objects from infinity to aclose distance while maintaining an excellent image-forming performance,employs a first group which is a divergent lens group having a focusingfunction, and a second group which is a convergent lens group disposedrearwardly of the first group. The first group includes a divergentforward portion, and a convergent rearward portion disposed with apredetermined spacing from the forward portion, the forward and rearwardportions being movable relative to one another for focusing. The firstand second groups are movable relative to each other to effect amagnification change. During the focusing upon an object at close rangeboth the forward portion and the rearward portion are moved toward theobject side, but the amounts of movement of the forward and rearwardportions are different, that is, the air space between these portions isincreased.

The invention will become more fully apparent from the followingdetailed description thereof taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and (b) show the basic construction of the present inventionas a Gauss system, FIG. 1(a) showing the focusing condition with respectto an infinite object and FIG. 1(b) showing the focusing condition withrespect to an object at a close distance;

FIG. 2 shows the lens arrangement of a first embodiment;

FIG. 3 shows the lens arrangement of a second embodiment;

FIG. 4 shows the lens arrangement of a third embodiment;

FIGS. 5, 6 and 7 illustrate aberrations with a photographingmagnification β=-0.25 on the closeup focal length side and the longestfocal length side of the respective embodiments; and

FIGS. 8(a) and 8(b), 9(a) and 9(b), and 10(a) and 10(b) illustratespherical aberration in a case where the close distance correction at anobject distance of 1 m is effected on the longest focal length side ofthe first, second and third embodiments, respectively, (a), and in acase where such correction is not effected (b).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The basic construction of the present invention is shown in FIGS. 1(a)and 1(b). FIG. 1(a) shows the focusing condition with respect to anobject at infinity, and FIG. 1(b) shows the focusing condition withrespect to an object at close range. Assume that when a light rayparallel to the optical axis is incident on a first lens group L₁, theincidence height in the forward portion L₁₁ thereof is h₁₁ and theincidence height in the rearward portion L₁₂ thereof is h₁₂. If theincidence height of this light ray in the rearward portion L'₁₂ is h'₁₂when the air space between the forward portion L₁₁ and the rearwardportion L₁₂ is increased, h'₁₂ >h₁₂ because the forward portion L₁₁ is adivergent lens group. The greater the value this incidence height has,the greater effect upon spherical aberration, and since the rearwardportion L₁₂ is a convergent lens group, the greater the value of theincidence height, and the more the correction of spherical aberration iseffected in the direction of under-correction.

In this lens system, the closer the object, the more sphericalaberration is over-corrected, but for the reasons set forth above, itbecomes possible to correct spherical aberration well in accordance withthe object distance if the air space d between the forward and rearwardportions of the first group is increased. The difference in amount ofmovement between the forward portion and the rearward portion should bedetermined by the difference in residual amount of spherical aberrationin that lens system.

However, since this lens system is a zoom lens system, the sphericalaberration on the long focal length side which occurs in such lenssystem must be adjusted in order to enhance the effect of theaforementioned close distance correction system in both the closeupfocal length condition and the long focal length condition. Thedesirable conditions for this are as follows:

    1.2|f.sub.1 |<f.sub.12 <2.8|f.sub.1 |(1)

and

    0.07<d/|f.sub.1 |<0.2                    (2),

where f₁ is the total focal length of the first group, f₁₂ is the totalfocal length of the rearward portion of the first group, and d is thespacing between the image side principal plane of the forward portion ofthe first group and the object side principal plane of the rearwardportion of the first group in the focusing condition with respect to anobject at infinity, or an infinite focal length.

Formula (1) is concerned with the power distribution in the forward andrearward portions of the first group. The spherical aberration on thelong focal length side tends to be essentially over-corrected at a closedistance, and therefore, it is necessary to maintain the sphericalaberration somewhat under-corrected with respect to an object atinfinity. If the lower limit of formula (1) is exceeded, the sphericalaberration on the long focal length side will become undulyover-corrected and this will make even the use of the aforementionedclose distance correction mechanism less effective. If the upper limitof formula (1) is exceeded, the spherical aberration will become undulyunder-corrected and the use of the aforementioned close distancecorrection mechanism will become meaningless.

Formula (2) is for suppressing the variation in spherical aberrationresulting from a variation in focal length. If the lower limit of thisformula is exceeded, it will become impossible to correct the variationin spherical aberration resulting from a variation in focal length. Ifthe upper limit of this formula is exceeded, the first lens group willbecome too thick and the image side principal plane of the first groupwill shift toward the object side to reduce the air space between thefirst group and the second group and reduce the range of movement of thetwo groups, thereby undesirably reducing the zoom ratio.

Unless the lens system is one which satisfies the conditions of formulas(1) and (2), the correction effect of spherical aberration, particularlythat on the long focal length side during focusing with respect to aclose distance object will be reduced.

According to the present invention as has been described above, theimage-forming performance for objects at a close distance has beenimproved and the closeup focal length has been greatly shortened to makeit possible to maintain the aberrations in a well-corrected condition onthe long focal length side of f=70 mm and for a magnification β=-0.25 ornear.

Embodiments of the present invention will hereinafter be described.

In a first embodiment, the lens arrangement of which is shown in FIG. 2,the forward portion L₁₁ of the first group L₁ comprises two negativemeniscus lenses each having its convex surface facing the object side,and the rearward portion L₁₂ comprises a positive meniscus lens havingits convex surface facing the object side.

In a second embodiment, as shown in FIG. 3, the forward portion L₁₁ ofthe first group L₁ comprises three components, in order from the objectside, i.e., a positive lens having its more sharply curved surfacefacing the object side, a negative lens having its more sharply curvedsurface facing the image side, and a negative meniscus lens having itsconvex surface facing the object side. The rearward portion L₁₂comprises a positive meniscus lens having its convex surface facing theobject side.

In a third embodiment, as shown in FIG. 4, the forward portion L₁₁ ofthe first group L₁ comprises three components, in order from the objectside, i.e., a negative meniscus lens having its convex surface facingthe object side, and a positive lens and a negative lens, each havingits more sharply curved surface facing the image side, and the rearwardportion L₁₂ comprises a positive meniscus lens having its convex surfacefacing the object side as in the first and second embodiments. Asregards the second group L₂, it may desirably comprise at least fivecomponents including a negative lens, as shown in the lens arrangementof each embodiment.

The numerical data of the respective embodiments are shown below. In thetables below, r, d, n and ν, respectively, represent the curvatureradius of each refractive surface, the center thickness of and the airspace between the lenses, the refractive index for d-line, and the Abbenumber for d-line. The subscripts represent the order from the objectside.

    ______________________________________                                        FIRST EMBODIMENT                                                              Total focal length of the entire system: f = 36.0˜68.6                  Angle of view: 2ω = 31°˜17.6° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 43.640                                                                         d.sub.1 = 1.5                                                                           n.sub.1 = 1.71300                                                                         ν.sub.1 = 53.9                            r.sub.2 = 25.862                                                                         d.sub.2 = 4.9                                                      r.sub.3 = 97.646                                                                         d.sub.3 = 2.3                                                                           n.sub.2 = 1.69680                                                                         ν.sub.2 = 55.6                            r.sub.4 = 34.089                                                                         d.sub.4 = close distance correcting spacing                        r.sub.5 = 32.807                                                                         d.sub.5 = 3.8                                                                           n.sub.3 = 1.80518                                                                         ν.sub.3 = 25.5                            r.sub.6 = 43.313                                                                         d.sub.6 = variable spacing                                         r.sub.7 = 38.800                                                                         d.sub.7 = 8.6                                                                           n.sub.4 = 1.62041                                                                         ν.sub.4 = 60.3                            r.sub.8 = -118.771                                                                       d.sub.8 = 2.5                                                      r.sub. 9 = 21.150                                                                        d.sub.9 = 4.9                                                                           n.sub.5 = 1.62041                                                                         ν.sub.5 = 60.3                            r.sub.10 = 67.565                                                                        d.sub.10 = 2.7                                                     r.sub.11 = -111.186                                                                      d.sub.11 = 4.2                                                                          n.sub.6 = 1.80518                                                                         ν.sub.6 = 25.5                            r.sub.12 = 20.265                                                                        d.sub.12 = 3.0                                                     r.sub.13 = -100.634                                                                      d.sub.13 = 3.2                                                                          n.sub.7 = 1.62588                                                                         ν.sub.7 = 35.6                            r.sub.14 = -29.367                                                                       d.sub.14 = 0.1                                                     r.sub.15 = 50.024                                                                        d.sub.15 = 2.5                                                                          n.sub.8 = 1.62588                                                                         ν.sub.8 = 35.6                            r.sub.16 = 110.281                                                            ______________________________________                                         Back focal distance: βf = 42.7˜65.2                                Close distance correction spacing: J.sub.4 = 10.7(∞)˜11.3         (β = -0.25)                                                              Variable spacing: d.sub.6 = 32.85˜0.05                             

    ______________________________________                                        SECOND EMBODIMENT                                                             Total focal length of the entire system: f = 36.0˜68.8                  Angle of view: 2ω = 31°˜17.4° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 61.849                                                                         d.sub.1 = 8.2                                                                           n.sub.1 = 1.60323                                                                          ν.sub.1 = 42.5                           r.sub.2 = -1037.164                                                                      d.sub.2 = 0.7                                                      r.sub.3 = 1000.000                                                                       d.sub.3 = 1.5                                                                           n.sub.2 = 1.67790                                                                          ν.sub.2 = 55.5                           r.sub.4 = 23.900                                                                         d.sub.4 = 6.8                                                      r.sub.5 = 178.734                                                                        d.sub.5 = 1.5                                                                           n.sub.3 = 1.71300                                                                          ν.sub.3 = 53.9                           r.sub.6 = 42.672                                                                         d.sub.6 = close distance correcting spacing                        r.sub.7 = 34.110                                                                         d.sub.7 = 3.9                                                                           n.sub.4 = 1.59507                                                                          ν.sub.4 = 35.6                           r.sub.8 = 81.925                                                                         d.sub.8 = variable spacing                                         r.sub.9 = 72.840                                                                         d.sub.9 = 3.5                                                                           n.sub.5 = 1.62041                                                                          ν.sub.5 = 60.3                           r.sub.10 = -72.840                                                                       d.sub.10 = 1.0                                                                          n.sub.6 = 1.80518                                                                          ν.sub.6 = 25.5                           r.sub.11 = -144.173                                                                      d.sub.11 = 0.1                                                     r.sub.12 = 26.644                                                                        d.sub.12 = 4.9                                                                          n.sub.7 = 1.51118                                                                          ν.sub.7 = 50.9                           r.sub.13 = 246.000                                                                       d.sub.13 = 0.1                                                     r.sub.14 = 20.743                                                                        d.sub.14 = 4.5                                                                          n.sub.8 = 1.51680                                                                          ν.sub.8 = 64.2                           r.sub.15 = 27.990                                                                        d.sub.15 = 3.9                                                     r.sub.16 = -370.855                                                                      d.sub.16 = 1.5                                                                          n.sub.9 = 1.80518                                                                          ν.sub.9 = 25.5                           r.sub.17 = 18.700                                                                        d.sub.17 = 5.2                                                     r.sub.18 = 64.660                                                                        d.sub.18 = 3.8                                                                          n.sub.10 = 1.64831                                                                         ν.sub.10 =  33.8                         r.sub.19 = -39.168                                                            ______________________________________                                         Back focal distance: βf = 43.7˜66.3                                Close distance correction spacing: d.sub.6 = 5.7(∞)˜6.2(.beta     = -0.25)                                                                      Variable spacing: d.sub.8 = 33.45˜0.65                             

    ______________________________________                                        THIRD EMBODIMENT                                                              Total focal length of the entire system: f = 36.0˜68.8                  Angle of view: 2ω = 31°˜17.4° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 50.379                                                                         d.sub.1 = 1.3                                                                            n.sub.1 = 1.74443                                                                         ν.sub.1 = 49.4                           r.sub.2 = 27.469                                                                         d.sub.2 = 6.3                                                      r.sub.3 = 670.373                                                                        d.sub.3 = 3.5                                                                            n.sub.2 = 1.51680                                                                         ν.sub.2 = 64.2                           r.sub.4 = -114.009                                                                       d.sub.4 = 0.1                                                      r.sub.5 = ∞                                                                        d.sub.5 = 1.8                                                                            n.sub.3 = 1.71300                                                                         ν.sub.3 = 53.9                           r.sub.6 = 32.531                                                                         d.sub.6 = distance correcting spacing                              r.sub.7 = 35.195                                                                         d.sub.7 = 3.4                                                                            n.sub.4 = 1.76182                                                                         ν.sub.4 = 26.5                           r.sub.8 = 57.902                                                                         d.sub.8 = variable spacing                                         r.sub.9  = 101.102                                                                       d.sub.9 = 3.0                                                                            n.sub.5 = 1.51680                                                                         ν.sub.5 = 64.2                           r.sub.10 = -763.611                                                                      d.sub.10 = 0.1                                                     r.sub.11 = 28.387                                                                        d.sub.11 = 6.4                                                                           n.sub.6 = 1.52000                                                                         ν.sub.6 = 70.1                           r.sub.12 = -449.780                                                                      d.sub.12 = 0.1                                                     r.sub.13 = 19.335                                                                        d.sub.13 = 5.9                                                                           n.sub.7 = 1.52000                                                                         ν.sub.7 = 70.1                           r.sub.14 = 37.463                                                                        d.sub.14 = 4.0                                                     r.sub.15 = -564.061                                                                      d.sub.15 = 1.4                                                                           n.sub.8 = 1.80518                                                                         ν.sub.8 = 25.5                           r.sub.16 = 16.279                                                                        d.sub.16 = 3.85                                                    r.sub.17 = 44.719                                                                        d.sub.17 = 4.1                                                                           n.sub.9 = 1.67270                                                                         ν.sub.9 = 32.2                           r.sub.18 = -56.453                                                            ______________________________________                                         Back focal distance: βf = 43.8˜68.7                                Close distance correction spacing: d.sub. 6 =                                 8.4(∞)˜9.0(β = -0.25)                                        Variable spacing: d.sub.8 = 28.93˜0.77                             

Various values forming the basic construction of each embodiment will beshown below.

    ______________________________________                                        First            Second     Third                                             Embodiment       Embodiment Embodiment                                        ______________________________________                                        f.sub.1 -59.966      -59.942    -53.000                                       f.sub.12                                                                              144.643      95.312     110.660                                       f.sub.12 /|f.sub.1 |                                                2.412        1.590      2.090                                         d       6.79         5.69       8.82                                          d/|f.sub.1 |                                                        0.11         0.09       0.16                                          ______________________________________                                    

The lens arrangements of the first, second and third embodiments areshown in FIGS. 2, 3 and 4, respectively. The aberrations with aphotographing magnification of β=-0.25 on the closest focal length sideand the longest focal length side of the respective embodiments areshown in FIGS. 5, 6 and 7.

Further, the spherical aberration in a case where the close distancecorrection at an object distance of 1 m (photographing magnificationβ=0.07) is effected on the longest focal length side of the first,second and third embodiments, respectively, (a), and in a case wheresuch correction is not effected (b) is shown in FIGS. 8, 9 and 10.

From these aberration figures, it will be evident that in all of theembodiments the correction of the various aberrations, especiallyspherical aberration, at a close distance is considerably improved andan excellent image-forming performance is maintained.

It is believed that the advantages and improved results furnished by thezoom lens system of the invention will be apparent from the foregoingdescription of preferred embodiments of the invention. Various changesand modifications may be made without departing from the spirit andscope of the invention as sought to be defined in the following claims.

I claim:
 1. A wide angle zoom lens system capable of photographingobjects from infinity to a close distance while maintaining an improvedimage-forming performance, said system comprising:a first divergent lensgroup including a divergent forward portion and a convergent rearwardportion disposed with a predetermined spacing from said forward portion,the forward and rearward portions being movable relative to each otherfor focusing; and a second convergent lens group disposed rearwardly ofsaid first group, said first and second groups being movable relative toeach other to effect a magnification change.
 2. The zoom lens systemaccording to claim 1, satisfying the following conditions:

    1.2|f.sub.1 |<f.sub.12 <2.8|f.sub.1 |

and

    0.07<d/|f.sub.1 |<0.2,

where f₁ is the focal length of said first group, f₁₂ is the focallength of the rearward portion of said first group, and d is the spacingbetween the image side principal plane of the forward portion of saidfirst group and the object side principal plane of the rearward portionof said first group during the focusing condition with respect to aninfinite object.
 3. The zoom lens system according to claim 2, whereinthe rearward portion of said first group includes a positive meniscuslens having its convex surface facing the object side.
 4. The zoom lenssystem according to claim 3, wherein the forward portion of said firstgroup includes two negative meniscus lenses, each having its convexsurface facing the object side.
 5. The zoom lens system according toclaim 3, wherein the forward portion of said first group includes, inorder from the object side, a positive lens having its more sharplycurved surface facing the object side, a negative lens having its moresharply curved surface facing the image side, and a negative meniscuslens having its convex surface facing the object side.
 6. The zoom lenssystem according to claim 3, wherein the forward portion of said firstgroup includes, in order from the object side, a negative meniscus lenshaving its convex surface facing the object side, a positive lens, and anegative lens having its more sharply curved surface facing the imageside.
 7. The zoom lens system according to claim 4 having the followingnumerical data:

    ______________________________________                                        Total focal length of the entire system: f = 36.0˜68.6                  Angle of view: 2ω = 31°˜17.6° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 43.640                                                                         d.sub.1 = 1.5                                                                           n.sub.1 = 1.71300                                                                         ν.sub.1 = 53.9                            r.sub.2 = 25.862                                                                         d.sub.2 = 4.9                                                      r.sub.3 = 97.646                                                                         d.sub.3 = 2.3                                                                           n.sub.2 = 1.69680                                                                         ν.sub.2 = 55.6                            r.sub.4 = 34.089                                                                         d.sub.4 = close distance correcting spacing                        r.sub.5 = 32.807                                                                         d.sub.5 = 3.8                                                                           n.sub.3 = 1.80518                                                                         ν.sub.3 = 25.5                            r.sub.6 = 43.313                                                                         d.sub.6 = variable spacing                                         r.sub.7 = 38.800                                                                         d.sub.7 = 8.6                                                                           n.sub.4 = 1.62041                                                                         ν.sub.4 = 60.3                            r.sub.8 = -118.771                                                                       d.sub.8 = 2.5                                                      r.sub.9 = 21.150                                                                         d.sub.9 = 4.9                                                                           n.sub.5 = 1.62041                                                                         ν.sub.5 = 60.3                            r.sub.10 = 67.565                                                                        d.sub.10 = 2.7                                                     r.sub.11 = -111.186                                                                      d.sub.11 = 4.2                                                                          n.sub.6 = 1.80518                                                                         ν.sub.6 = 25.5                            r.sub.12 = 20.265                                                                        d.sub.12 = 3.0                                                     r.sub.13 = -100.634                                                                      d.sub.13 = 3.2                                                                          n.sub.7 = 1.62588                                                                         ν.sub.7 = 35.6                            r.sub.14 = -29.367                                                                       d.sub.14 = 0.1                                                     r.sub.15 = 50.024                                                                        d.sub.15 = 2.5                                                                          n.sub.8 = 1.62588                                                                         ν.sub.8 = 35.6                            r.sub.16 = 110.281                                                            ______________________________________                                         Back focal distance: βf = 42.7˜65.2                                Close distance correction spacing: d.sub.4 = 10.7(∞)˜11.3         (β = 0.25)                                                               Variable spacing: d.sub.6 = 32.85˜0.05                             


8. The zoom lens system according to claim 5 having the followingnumerical data:

    ______________________________________                                        Total focal length of the entire system: f = 36.0˜68.8                  Angle of view: 2ω = 31°˜17.4° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 61.849                                                                         d.sub.1 = 8.2                                                                           n.sub.1 = 1.60323                                                                          ν.sub.1 = 42.5                           r.sub.2 = -1037.164                                                                      d.sub.2 = 0.7                                                      r.sub.3 = 1000.000                                                                       d.sub.3 = 1.5                                                                           n.sub.2 = 1.67790                                                                          ν.sub.2 = 55.5                           r.sub.4 = 23.900                                                                         d.sub.4 = 6.8                                                      r.sub.5 = 178.734                                                                        d.sub.5 = 1.5                                                                           n.sub.3 = 1.71300                                                                          ν.sub.3 = 53.9                           r.sub.6 = 42.672                                                                         d.sub.6 = close distance correcting spacing                        r.sub.7 = 34.110                                                                         d.sub.7 = 3.9                                                                           n.sub.4 = 1.59507                                                                          ν.sub.4 = 35.6                           r.sub.8 = 81.925                                                                         d.sub.8 = variable spacing                                         r.sub.9 = 72.840                                                                         d.sub.9 = n.sub.5 = 1.62041                                                                          ν.sub.5 = 60.3                           r.sub.10 = -72.840                                                                       d.sub.10 = 1.0                                                                          n.sub.6 = 1.80518                                                                          ν.sub.6 = 25.5                           r.sub.11 = -144.173                                                                      d.sub.11 = 0.1                                                     r.sub.12 = 26.644                                                                        d.sub.12 = 4.9                                                                          n.sub.7 = 1.51118                                                                          ν.sub.7 = 50.9                           r.sub.13 = 246.000                                                                       d.sub.13 = 0.1                                                     r.sub.14 = 20.743                                                                        d.sub.14 = 4.5                                                                          n.sub.8 = 1.51680                                                                          ν.sub.8 = 64.2                           r.sub.15 = 27.990                                                                        d.sub.15 = 3.9                                                     r.sub.16 = -370.855                                                                      d.sub.16 = 1.5                                                                          n.sub.9 = 1.80518                                                                          ν.sub.9 = 25.5                           r.sub.17 = 18.700                                                                        d.sub.17 = 5.2                                                     r.sub.18 = 64.660                                                                        d.sub.18 = 3.8                                                                          n.sub.10 = 1.64831                                                                         ν.sub.10 = 33.8                          r.sub.19 = -39.168                                                            ______________________________________                                          Back focal distance: βf = 43.7˜66.3                               Close distance correction spacing: d.sub.6 = 5.7(∞)˜6.2(.beta     = -0.25)                                                                      Variable spacing: d.sub.8 = 33.45˜0.65                             


9. The zoom lens system according to claim 6 having the followingnumerical data:

    ______________________________________                                        Total focal length of the entire system: f = 36.0˜68.8                  Angle of view: 2ω = 31°˜17.4° F-number:             ______________________________________                                        3.5                                                                           r.sub.1 = 50.379                                                                         d.sub.1 = 1.3                                                                            n.sub.1 = 1.74443                                                                         ν.sub.1 = 49.4                           r.sub.2 = 27.469                                                                         d.sub.2 = 6.3                                                      r.sub.3 = 670.373                                                                        d.sub.3 = 3.5                                                                            n.sub.2 = 1.51680                                                                         ν.sub.2 = 64.2                           r.sub.4 = -114.009                                                                       d.sub.4 = 0.1                                                      r.sub.5 = ∞                                                                        d.sub.5 = 1.8                                                                            n.sub.3 = 1.71300                                                                         ν.sub.3 = 53.9                           r.sub.6 = 32.531                                                                         d.sub.6 = close distance correcting spacing                        r.sub.7 = 35.195                                                                         d.sub.7 = 3.4                                                                            n.sub.4 = 1.76182                                                                         ν.sub.4 = 26.5                           r.sub.8 = 57.902                                                                         d.sub.8 = variable spacing                                         r.sub.9 =  101.102                                                                       d.sub.9 = 3.0                                                                            n.sub.5 = 1.51680                                                                         ν.sub.5 = 64.2                           r.sub.10 = -763.611                                                                      d.sub.10 = 0.1                                                     r.sub.11 = 28.387                                                                        d.sub.11 = 6.4                                                                           n.sub.6 = 1.52000                                                                         ν.sub.6 = 70.1                           r.sub.12 = -449.780                                                                      d.sub.12 = 0.1                                                     r.sub.13 = 19.335                                                                        d.sub.13 = 5.9                                                                           n.sub.7 = 1.52000                                                                         ν.sub.7 = 70.1                           r.sub.14 = 37.463                                                                        d.sub.14 = 4.0                                                     r.sub.15 = -564.061                                                                      d.sub.15 = 1.4                                                                           n.sub.8 = 1.80518                                                                         ν.sub.8 = 25.5                           r.sub.16 = 16.279                                                                        d.sub.16 = 3.85                                                    r.sub.17 = 44.719                                                                        d.sub.17 = 4.1                                                                           n.sub.9 = 1.67270                                                                         ν.sub.9 = 32.2                           r.sub.18 = -56.453                                                            ______________________________________                                         Back focal distance: βf = 43.8˜68.7                                Close distance correction spacing: d.sub.6 = 8.4(∞                      )˜9.0(β = -0.25)                                                   Variable spacing: d.sub.8 = 28.93˜0.77                             